Probe Measurements of Ash Deposit Formation Rate and Shedding in a Biomass Suspension-Fired boiler

Muhammad Shafique Bashir, Peter Arendt Jensen, Flemming Frandsen, Stig Wedel, Kim Dam-Johansen, Johan Wadenbäck, Søren Thaaning Pedersen

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Abstract

The aim of this study was to investigate ash deposit formation rate, heat uptake reduction and deposit
removal by using advanced online ash deposition and sootblowing probes in a 350 MWth suspension-fired boiler,
utilizing wood and straw pellets as fuel. The influence of fuel type (straw share in wood), probe exposure time, probe
surface temperature (500, 550 and 600 oC) and flue gas temperature (600 - 1050 oC) on ash deposit formation rate,
heat uptake by the probe, the fly ash and deposit characteristics, and deposit removal have been investigated. The
results indicated that increase in flue gas temperature increased the ash deposit formation rate. It was also found that
probe heat uptake reduction was not strongly sensitive to the deposit mass load on the probe. This indicated that the
heat transfer from the flue gas to the probe was dominated by the rear side, where little material was accumulated on
the probe if the deposit mass load was very high on the flue gas facing side of the probe. Results of deposit removal
by using sootblowing probe indicated that probe exposure time and surface temperature significantly influence the
Peak Impact Pressure (PIP) needed to remove the deposits. The video recordings of all deposit probe experiments
revealed that deposit shedding was primarily through debonding from the surface of the tubes in the superheater
region. Chemical analysis of fly ashes indicated that during suspension-firing of straw and wood, the fly ashes were
rich in Si, K, Ca and Cl, but the relative percentage of volatile elements (K, Cl and S) was much less compared to
grate-firing conditions. The chemical analysis of the deposits showed that the inner most layer was dominated by
contents of K, Cl and S compared to the upper layers rich in K, Si and Ca
Original languageEnglish
Publication date2011
Number of pages14
Publication statusPublished - 2011
Event19th European Biomass Conference and Exhibition - Berlin, Germany
Duration: 6 Jun 201110 Jun 2011
http://www.conference-biomass.com/Previous-Events.70.0.html

Conference

Conference19th European Biomass Conference and Exhibition
CountryGermany
CityBerlin
Period06/06/201110/06/2011
Internet address

Keywords

  • Biomass
  • Straw
  • Wood
  • Fly Ash
  • Fouling
  • Slaggin

Cite this

Shafique Bashir, M., Jensen, P. A., Frandsen, F., Wedel, S., Dam-Johansen, K., Wadenbäck, J., & Pedersen, S. T. (2011). Probe Measurements of Ash Deposit Formation Rate and Shedding in a Biomass Suspension-Fired boiler. Abstract from 19th European Biomass Conference and Exhibition, Berlin, Germany.